Three-dimensional imaging can be classified into two major groups according to the quantity of information required to record the images: (1) binocular stereoscopic imaging, and (2) autostereoscopy or three-dimensional spatial imaging. See Takanori Okoshi, Three-dimensional imaging Techniques, Academic Press Inc. New York pp.4-28 (1976). The binocular viewers, parallax stereogram's, lenticular-sheet binocular stereoscopic pictures, and binocular displays using polaroid glasses or color filters belong in the first group. Parallax panoramagrams, lenticular-sheet three-dimensional imaging, projection type three-dimensional displays, and integral photography etc. belong in the second group.
In the second group, autostereoscopy or 3-D spatial imaging, a three-dimensional image is created by a series of 2-D images of an object captured from different perspectives, and therefore the 3-D image so produced contains multiple-angle information about the object. In all of these 3-D spatial imaging techniques, the most important parameter, called "base", impacts directly on the 3-D effect and the quality of the autostereoscopic display produced. "Base" is defined as the distance between adjacent camera placements from which the pictures of the object are taken. With the base properly adjusted, the overall 3-D spatial quality is produced. If the base is too large, the excessive spatial parallax will cause the image being viewed to degrade the quality of the 3-D effect due to flipping and smearing. If the base is too small, the reduction in parallax will cause the image being displayed to be viewed as somewhat flattened and therefore less 3-D sensational.
Lo et al U.S. Pat. No. 3,960,563 suggests that the maximum spatial parallax between two adjacent images should be controlled so as not to exceed five lenticules in width if the width of the lenticule in the picture is greater than 5 mils, or should not exceed ten lenticules in width if the width of the lenticule is smaller than 5 mils. This technique of trying to control the spatial parallax between an image pair by setting the number of lenticules between an image pair of the same object is not very effective under some circumstances.
U.S. Pat. No. 3,908,112 attempts to solve the problem by a special calculator for use in taking stereoscopic pictures. This calculator is designed to obtain the desired parallax value by determining the location of the camera relative to the foreground element, the background element and the key subject matter element of the scene to be photographed.
However, in spite of these prior art attempts at solving the problems of 3-D spatial imaging, the major difficulty remains in getting both the middle key subject image with perfect 3-D effect while at the same time producing large depth of field for both the background and foreground without causing "flipping".
It is therefore the principal object of the invention to provide a method for overcoming this major difficulty and thereby dramatically improving the 3-D effect of the image. In particular, it is an object of the invention to provide a synthesized depth of field and sensational three-dimensional effect.